Pest description and crop damage This aphid-like insect feeds on newly growing needles. Adelgids appear as woolly or cottony tufts on the undersides of needles, with heavily infested trees appearing "frosted" or flocked. Small purplish insects are found underneath the cottony tufts.
Adelgid feeding can cause needles to become distorted or bent and yellowed. Infested needles turn brown and sometimes drop prematurely. This pest is a serious concern in Christmas tree plantations, but is less important in the landscape. Cooley spruce gall adelgids also infest spruces, but cause distinctive galls on spruce that are not seen on Douglas-fir.
Plant Douglas-fir and spruce as far apart as possible.
Chemical Control of Nursery Pests
Apply to control crawlers after eggs hatch, usually at the time when new tip growth is expanding.
See "Douglas-fir" in:
Christmas Tree Plantation Pests
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 76).